The present invention relates to open end wrenches, and more particularly to an improved structure of an open end wrench which is practial for grasping and turning normal bolts and nuts of different specifications as well as worn-out bolts and nuts of different specifications.
An open end wrench is handy tool intensively used for grasping and turning bolts and nuts. A variety of open end wrenches have been disclosed having teeth, raised portions or rough grasping faces at the jaws for grasping and turning normal bolts and nuts as well as worn-out bolts and nuts. Exemplars of conventional open end wrenches are shown in FIGS. from 1 to 13. The open end wrench shown in FIGS. 1, 2, and 3 has two flat raised portions at the jaws. This structure of open end wrench is functional for turning normal bolts and nuts as well as slightly worn-out bolts and nuts. However, it can not positively grasp and turn excessively worn-out bolts and nuts. FIGS. 4, 5, 7,8, 9, 10 and 11 show other different designs. These designs can grasp and turn bolts and nuts of different sizes. However, these designs can not positively grasp and turn excessively worn-out bolts and nuts. FIG. 6 shows another design of open end wrench which is similar to the open end wrench shown in FIGS. 1 to 3. FIG. 12 shows an open end wrench having rough faces at the jaws. FIG. 13 shows an open end wrench having teeth at the jaws. The open end wrenches shown in FIGS. 12 and 13 can positively grasp and turn normal bolts and nuts, however they tend to slip when turning an excessively worn-out bolt or nut.
It is one object of the present invention to provide an open end wrench which is practical for grasping and turning hexagon head bolts and hexagon nuts as well as square head bolts and square nuts. It is another object of the present invention to provide an open end wrench which is practical for grasping and turning normal bolts and nuts of different specifications as well as worn-out bolts and nuts of different specifications. According to the present invention, the open end wrench comprises a mouth defined between two jaws and nest thereof, a flat raised portion and a longitudinal series of teeth respectively raised from the two jaws inside the mouth. The longitudinal series of teeth including seven teeth, and the center of the raised portion being in alignment with the center of the mouth and the middle tooth of the longitudinal series of teeth. The distance from the center of the mouth of the nest being equal to the distance from the center of the polygonal head of the polygonal head bolts to be turned to the corner of the bolts. The line between the front end of the raised portion and the second tooth of the longitudinal series of teeth being parallel to the line between the rear end of the raised portion and the second to last tooth of the longitudinal series of teeth, the longitudinal length of the longitudinal series of teeth being 0.56 of the width of the mouth, and the distance from the front end of the longitudinal series of teeth to the nest being 0.89 of the width of the mouth.